Sales order deletion

I am creating SO.Based on this sales order a production order is created.When i am trying to create a delivery there is a credit block.I remove the credit block & delete one line item in SO.But when i delete one item in sales order,the system sets deletion indicator for the prodcution order related to all the sales order.

How to overcome the issue of preventing the deletion indicator being set for all these production orders which are connected to the SO.